Aeronautical propeller



.Fufiy 31, E923- 1,463,556

.5. A. REED AERO NAUT I CAL PROPELLER Filed May 26, 1920 eration.

?atented July 31, 1923 snares iaease era-rear reins.

AERONAUTICAL JPROEELLEE.

Application filed Hay 26, 1920. Serial No. 384,293.

To all whom it may concern:

Be it known that i, SYLvANUs ALBERT 'Rnnn, a citizen of the United States, residing at New York city, in the county of New the design or construction and operation of my improved construction of propellers first, the limit of rupture, andsecond, the limit of propeller etiiciency measured by the York and ,State of New York, have invented ratio of thrust at stated flying velocities to certain new and useful Improvements in Aeronautical Propellers, of which; the following is sucha full, clear, and exact description as will enable any one skilled in the art to make and use the same.

'iy invention relates to propellers for air craft and flying machines and discloses a novel principle for obtaining the necessary rigidity of the propeller blades to resist the stresses, thereby making possible the use of much thinner blades than heretofore with a ain in efliciency.

'eretofore aeronautical propellers have been made of material such as wood or metal constructed tobe structurally rigid against operative stresses, such rigidity usually being substantially sufficient, even when at rest, to resist tangential axial and radial stresses which would occur in full speed 0p- It is obvious that when an aero nautical propeller, say eight feet diameter, is operated at say 1200' revolutions per minute, centrifugal force adds to the structural rigidity due to the form of the propeller, a quasi or virtual or dynamic rigidity from the radial tension due to centrifugal forte, and this added rigidity is a contingent advan tage, but hitherto not regarded as an element which would justify omitting any considerable percentage of the elements providing static or intrinsic rigidity. This has much justification where the rotative speeds v do not much exceed 1000 revolutions per minute. If, however, high rotative speeds are used, such for example, as say 5000 to 15000 revolutions per minute, the centrifugal t'orce becomes such a large factor that a progressively less necessity exists for structural or intrinsic rigidity and I have ascertained by many experiments, and as can be easily calculated from well known laws of mechanics, that at certain rotative speeds, a stage or condition is reached where structural or intrinsic rigidity can be largely and to a substantial extent discarded in the design of the propeller and its construction, and reliance placed mainly upon the quasi or virtual rigidly of kinetic character due to centrifugal force.

There are twO limiting considerations in torque. I have found regarding the first, that by using with propeller blades of thin material the familiar method of tapering the thickness of the blade from hub to tip, very large rotative velocities may safely be used with propellers of diameter sufiicient for practical use, and regarding the second, that by substituting thin material blades for blades having the bulky interior portions of structurally or intrinsically rigid propellers, the great reduction in air resistance produces at these high tip velocities efficiencies which compare very favorably with those of the propellers of the customary bulky and massive forms operated at customary speeds.-

My invention consists in the various novel and peculiar constructions and arrangements of parts as herein set forth and particularly pointed out in the claims, and I have illustrated types of my invention in the accompanying drawings which are some what diagrammatic in parts and wherein p i. endeavor to clearly show the relatively thin character of the propeller blades the cross-section of which maybe varied. In

power indicated in said figure, the propeller being a double-bladed one and the view being taken edgewise thereof.

Fig. 2, is a broadside view of the propeller shown i Fig. l, and shown as detached.

'Fig. 3, is an enlarged perspective view of the central part of the two-bladed propeller with the outer portions of the blades broken away, together with two clamping sections of the hubshown as spaced apart in relative blades are set or anchoredfin the he at a suitable pitch-angle and in any suitable ice form of the invention, in which sef arate manner, the

ceiving :the drive-shaft 5, driven by a suitable source of power indicated at 6, such as an' lnternal combustion engine, or steamengine or other well known form of motor.

The propeller just described contains its own hub 3, and may be used without additional' hub structure, but it may be attached to the usual tubular metal hub member customarily employed with wooden propellers and the same mounted on the propeller shaft. I prefer, however, to provide the propeller hub 3, with additional sectional members made in two clamping sections 7 and 8, each having a central opening for the .shaft5, and each formed with key-ways 9, forreceiving the key 10, fixed on the shaft, the central part 3, of the propeller being also formed with key-ways 11, for receiving the shaft key 10, thereby strengthening the assembled parts. In order to give the blades 1 and 2, the necessary pitch-angle, ll bend or twist the central connecting part 3 as indicated at 12, in a manner suitable to provide such pitch-angle at the outer part of each blade. Thus a simple twist would accomplish the same result, but in order to avoid possible unequal strain on the material involved by twisting metal cold, ll prefer to use the bend 12, which is shown as a geometrical double bend of such shapefland stantiall character as to provide each'blade with the same pitch-angle, and obviously the shape or form of said bend may be varied as desired, so long as the DQTQSSEJ-Iy pitch-angle is obtained, as indicated in the drawings.

It will also be noted that each blade has its pitch or blade angles diminishing helically or screw-like from root to tip, as indicated in Fig. 1, which shows an edge view in elevation of my propeller, the said construction giving the effect in-said view of a convergence from root to tip of the edges of the blade, which Fig. 2,- showsof sub uniform width. The c amping-faces 13 and 1t, ofthe respective hub sections 7 and 8, are shaped to conform to and to truly fit the pitch-angle bend 12, upon the opposite sides of the central part 3, and they are counter-parts of each other. The hub-sections are provided with bolt-holes 15 and 16., respectively, which register with a similar set of holes 17, in the hub-part 3, and, receive the bolits 18,

neelaeea by means of which the said parts are securey fastened together, as indicated inFig. l. bus the hub members: serve to hold and to assist in retaining in shape the one-piece double-bladed propeller and the blades external to the hub are maintained at the desired pitch-angle.

The blades taper in thickness from hub to tip, as indicated in the drawings, and the rear side is somewhat flat as at 19, while the forward face is slightly bowed or curved as at 20, whilethe edges are relatively sharp, as indicated at 21, but of course this form maly be varied as found expedient. n Fig. 4, I show a modified form of my propeller in which there are four blades 22, 23, 24: and 25, arranged equal distances apart in radial relation and made in one piece of material. This is secured to a hub 32-33 by means of bolts 27, and the hub is keyed to the shaft 28, which drives the propeller. The pitch-angle is given each blade by bending it near the hub on oblique lines 30, 31, in opposite directiens, while the central portion 26 is uiibeht; The hub is formed in two sections 32 a11d 33, which are shaped or molded on theirinner faces to conform to the series of bends in the respective blades as well as the blades, and areclamped against the blades by the bolts 27, the section 33 being shown as broken away.

Fig. 5, shows a modified form of blade 42, which instead of being integral with its opposite blade, is for ed separate'and is secured in any suitabl manner to the hub 43, at an angle' such as to give the blade the requisite pitch-angle.

ll make my improved blade relatively thin and thinner than customary throughout, thereby dispensing with a large amount of material which has been required heretofore to give the blade the proper amount of rigidity, and which thin blade when operated at the high speeds herein referred to receives a degree of rigidity imparted thereto by radial tension sufficient to make it practically operative.

By dispensing with the bulk necessary for intrinsic rigidity, my improved propeller wastes less power in friction and air resistance than propellers of the intrinsically lly'thus providing a propeller which can be operated efficiently at tip velocities much higher than those that have been heretofore employed, the way is opened for the use of motors of higher rotational speed,.withroe ' rigid type and it is therefore more efficient.

out the necessity of gearing down to a hith-' erto limited rate of rotation for the propeller shaft or for propellers of greater diameter at customary rotative speeds. With this limitation removed motors of higher efiiciency, that is greater power per unit of. weight, can be used, and my improved propeller is especially suited for direct connection to a steam turbine engine which is thereby better adapted for use as a directdrive aerial motor.

The thinness of the blades of my propeller also affords an advantage over propellers of the intrinsically rigid type, in respect to their superior adaptability to assemblage as multi-blade propellerseither radial or tandem on the same shaft. Thus two twoblade propellers may be crossed at rightangles quite close together on the same shaft, or three or more assembled in a similar way to produce a multi-blade propeller. Or propellers may be strung one in front of the other at intervals, that isto say in tandem, without occupying as much of the length of the propeller shaft as would be required for a similar arrangement with propellers of the intrinsically rigid type.

I have found that by the assemblage of my propellers in both the radial and tandem manner I obtain an increased absorption of the motor power and delivery of same in the form of useful thrust, without an decrease of efliciency and with the occupation of much less space than would be the case with a similar grouping of propellers of the intrinsically rigid type. i

My improved propeller may have its blades made of metal, or alloy of metal, or wood, or a suitable composition, and the material used may be flexible, pliable, ductile or malleable, the important requisite being that when made of the required thinness the blade will fulfill the essential requirements herein stated. I have used flat steel and also aluminum in making my improved propellers.

My improved propeller may be made from suitable sheet metal, or by forging or casting the same, and it can be manufactured at a lower cost than other forms'of'aeronautical propellers. It can be rapidly and cheaply made by stamping it directly from the sheetmetal in completed form except for minor finishing. v 'It will be observed that while,'for the purposes of illustration, I have herein set forth specific embodiments of my invention for utilizing a high degree of radial tension due to centrifuge force as means for creating and maintalning suficient virtual rigidity in thin propeller blades to make them practiaware that many changes and modifications may be e in the difierent features thereof, without, however, departing from the spirit of my insvention.

The term relativelythin as used herein, is intended to define a body whose maximum thickness is that of a metal plate as distinguished from the thinness of a metal sheet, on the one hand, and the thickness of a metal bar or like bulky body, on the other. It is to'be no that the flexing strs of operation are slight at slow rotative speeds, as while getting up speed, the centrifugal force being also slight, but the degree of flexibility of my blades at various points is so proportioned that at every speed the centrifugal force supplements the intrinsic rigidity sufficiently for the necessary actugall rigidity to meet the stresses at that spee While I have herein described my invention as particularly applicable for use in connection with areonautics, it is obvious that the same is applicable for use in any field in which air propulsion or blasts can be used.

Having thus described my invention, what I claim and desir to secure by Lette Patent is:.

1. An aeronautical propeller having single piece blades'constructed of material of such thinness as to require dependence partly but mainly upon the radial tension exerted by centrifugal force to maintain the blades in operative form or'shape.

An aeronautical propeller having single piece blades of materia-lwhich is flexible and dependent partly but mainly upon centrifugal force to gi've the blades suflicient rigidity to substantially overcome lateral deflecting forces tending to reduce efficiency.

3. An aeronautical propeller having single piece blades dependent for resistance to fiexure caused by air partly but mainly upon the virtual rigidity imparted by radial tension due to centrifugal force.

4. An aeronautical propeller having onepiece blades dependent for resistance to upon thevirtual rigidity imparted by radial I 4 tension due to centrifugal force, and means combined therewith for rotating the propeller at a rate adequate to cause centrifugal force of the degree. necessary for sufficient virtual rigidity.

5. An aeronautical propeller the thickness of whose blades does not exceed substantially one-seventy-fifth of their lengths, the propeller being so bent or twisted that the said blades are Mdilv deflected pitch-wise.

6. An aeronautical neckless propeller whose blades have a ratio of thickness to length not exceeding substantially one-' seventy-fifth and have a relatively thin root portion sufficiently rigid to with-stand deformation and a relatively elastically flexible outer portion and with blade pitch-angles diminishing helically from root to tip.

7. A one-piece aeronautical neckless propeller made of metal and whose blades are relatively thin throughout their lengths and have a progressively increasing elastic flexibility from root to tip.

8. A one-piece aeronautical propeller having arelatively thin and wide and rigid central connecting portion and relatively flexible outer portions, said central portion being rigid independently of its mounting- .means.

9. A metal aeronautical propeller Whose blades are relatively thin throughout their lengths and have as great a width at the axial region as at any other point throughout their lengths and with blade pitchangles diminishing helically from roots to tips. a

10. A metal aeronautical propeller whose blades are relatively thin throughout their lengths and whose outer portions are of no greater width than the axial region and with blade pitch-angles diminishing helically from roots to tips.

11. A metal aeronautical propeller whose blades are relatively thin throughout their lengths and substantially Wide and non-cylindrical at the axial region and are no nar rower-at the axial region than at any part of the outer portions and with blade pitchangles diminishing helically from roots to tips.

12. A one-piece aeronautical propeller whose blades are relatlvely thin with'a root portion sutliciently rigid to withstand def-' ormation byair during rotation and with the outer portion relatively flexible and dependent mainly upon centrifugal force for ,suiiicient rigidity against deforming stresses during operation. 1 I

13. A metal aeronautical propeller whose blades are relatively thin and taper in thickthe kinetic or virtual rigidity due to centrifugal force a ratio which is large at or near the axis and diminishes progressively to a small figure at the tips and with blade pitch-angles diminishing helically front roots to tips.

15. An aeronautical propeller whose blades have as great a width in the axial region as at any other point throughout their'lengths and are soflconstructed and proportioned that theirstructural or intrinsic rigidity for resisting the deforming stresses of operation bears to the kinetic or virtual rigidity due to centrifugal force a ratio al) which is large at or near the axis and diminishes progressively towards. the tips to a small figure thereat.

16. A single piece metal aeronautical propeller twisted or formed to give its blades a screw-pitch and whose blades are tapered in thickness substantially from the axial re= gion to the tips to a thinness increasing to such a degree of resilient flexibility beyond substantially half-blade length as to depend for their rigidity against deflecting forces mainly upon centrifugal force during operation.

17. A one-piece aeronautical propeller made of metal and relatively thin throughout and having a rigid central or bladeconnecting portion and relatively flexible outer portions, whose pitch-angles diminish progressively from roots to tips. I

18. An aeronautical propeller having blades shapedto a definite pitch and tapered in thinness towards the tips to such a degree of resilient flexibility that the propeller relies for adequate rigidity during operation partly butrmainly upon centrifugal force, and Whose opposite blades are rigid.- ly united centrally by extending one of the other with a reversal of blade-angle with the radial plane effected by compound bends equivalent to a twist continuing the lea ling edge ot each blade as the trailing edgeof the other.

19. An aeronautical propeller havin blades shaped to a definite pitch and tapere in thinness towards the tips to such a degree that they rely for adequate rigidity during operation partly but mainly upon comparison with the thickness in said plane,

for effective transmission oftorque.

In testimony whereof, I have hereunto set my hand'in the presence of the two subscrib ing witnesses.

S. ALBERT REED. Witnesses:

'Gronen'C. Kenna, LEoN MALRAISON., V

through the axis of rotation to continuation r ice 

